1. Field of the Invention
The present invention relates to a plate bending machine, and, in particular, to a plate bending machine such as a press brake provided with a manipulator capable of handling a plate which is subjected to a bending process in a bending machine, and to a plate bending machine provided with a plate position detecting device capable of detecting a position of the plate which is being handled by the manipulator and being subjected to the bending process.
2. Description of the Prior Art
Conventionally, a manipulator has been developed for automatically handling the workpiece in a plate bending machine such as a press brake, where a plate bending operation is performed, in order to automate this process.
A conventional manipulator, which is usually equipped with an industrial robot, is generally set up in a specified position in front of the bending process machine. In this type of manipulator the arm is installed on a support column in a manner to allow both free vertical and rotary movement and also to provide free telescopic motion, and rotation. A plate clamping device is provided on the end of the arm for freely grasping a workpiece.
In a conventional manipulator with the abovementioned configuration, for the plate clamping device to have a wide range of movement the arm must be long. Therefore, the overall configuration results in a large manipulator, which is a drawback. In addition, the positioning of a plate in the plate bending device of the plate bending process machine is performed entirely by the manipulator. It is therefore necessary to construct a high-precision manipulator to improve the precision of the positioning of the plate. This leads to the problem of excessively high production costs.
The inventor of the present invention, with due consideration to these problem areas, has disclosed in Japanese Patent application No. Sho-62-313760 an improved manipulator for handling plate material in a plate bending machine such as the press brake described. This manipulator grasps the plate material and causes the clamped plate to rotate through 180 deg with respect to the plate bending machine. Accordingly, in the case where the plate is bent in more than one place, successive scheduled bending points can be provided to the plate bending machine, depending on the bending stage.
However, in carrying out a high precision bending process in such a bending machine, it is necessary for the plate to be accurately positioned with respect to the plate bending machine. In achieving such accurate positioning by means of the manipulator mechanism only, the problem arises that the manipulator must be constructed with an extremely big degree of precision. This, in turn, leads to the problem of an extremely high cost for the manipulator.